Dear Doctor: My boyfriend laughs when I turn down the car stereo when I'm trying to find a new address, but I've seen his dad do the same thing when he's changing lanes on the freeway. Why does the quiet make you feel like you can see better?
Dear Reader: Your boyfriend may have fun teasing you, but we'd be surprised if there haven't been similar instances in his own life.
The scenarios you describe, which require you to evaluate incoming data and make split-second decisions, suck up a lot of mental energy. Researchers refer to this as "cognitive load." Eliminating a distraction such as sound can help with concentration by reducing the cognitive load. That's because, much like a computer, our brain's capacity to engage in multiple tasks is finite.
To understand why, it helps to appreciate the complexities of the human brain. It's made up of three major parts -- the cerebrum, cerebellum and brainstem. The largest and topmost part is the cerebrum, which is divided into left and right hemispheres. It deals with learning, emotions, reasoning and fine motor skills, and it interprets the flood of data from the five senses. Tucked beneath is the much smaller cerebellum, which oversees muscle movement, balance and posture. Acting as a relay center between the two and the spinal cord is the brainstem, which also oversees the staying-alive stuff we don't think about but can't live without. This includes breath, heartbeat, swallowing, sleep cycles and temperature control.
The three areas of the brain, plus the spinal cord, make up the central nervous system. It regulates movement, thought and emotion. It's why you're able to find that new address. But while it seems as though we can concentrate on multiple things at once, the brain handles tasks sequentially. It's just making the switch so swiftly, in mere nanoseconds, that it feels like we're multi-tasking. Once you're hunting for a street sign, though, or gauging car lengths in fast-moving traffic, all of the collecting and interpreting of data by the central nervous system reaches critical mass. That cognitive load we talked about earlier gets to be too great. Turning down the radio removes enough incoming data to make it easier to concentrate.
A small study in Sweden looked into this phenomenon several years ago. Researchers had each of 32 participants perform an easy visual task and a challenging visual task. They were also instructed to ignore the audio -- a random sequence of sounds -- that was playing. The subsequent MRI tests revealed that when participants concentrated on a visual task, there was a decrease in the responsiveness of the auditory nerves. Basically, the brain itself was turning down the volume.
The takeaway here is that when our inner mute button can't adequately remove the auditory distraction, our brain kicks in and we decide to turn down the car stereo. We're adjusting our environment so the most important task -- finding the address or safely merging onto the freeway -- has a better chance of getting accomplished.
Eve Glazier, M.D., MBA, and Elizabeth Ko, M.D.